Thermal time delay



Patented June 7, (1949 (Chipz-.7.0)

1 Claim.

This invention relates to safety `devices for pro., jectile fuzes and more specifically to a novel thermal safety delay device for use in fuzes for rotating projectiles.

An ohiectgof this invention is to provide a safety delay device for fuzes, which comprises a safety gate normally separating the detonator 'squibg` from the usual booster charge and secured in its closed o r safe position-,hva fusible element.

heating charge is ignited in response to the farce. f.. setbackwhen the pristile is fired. and after, @predetermined length@ time, the fusible element becomes melted or suiciently softened by the heat to permit centrifugal force to move the safety gate to an unarmed position.

A further object of this invention is to provide a thermal safety delay device which will withstand dropping land tumbling, and which will not operate to arm the fuze until acted upon successively by a force of setback and centrifugal force.

A further object of this invention is to provide a thermal safety delay 4device which is compact, reliable, simple, and adaptable to large scale production.

Other objects and many of the attendant advantages of this invention will Ibe appreciated readily as the same becomes understood by reference to the following detailed description, when considered in connection with the accompanying drawings, wherein:

Fig. 1 is an axial sectional view of one form of the new thermal safety delay [device in safe position;

Fig. 2 is a similar view of the device in its armed position; and

Fig. 3 is a fragmentary transverse sectional view taken in plane 3-3 of Fig. 1.

In the drawing, the numeral I0 represents the body of the device. The body is of cylindrical shape and is designed to fit tightly within a projectile casing with the upper end of the body toward the nose of the projectile. An axial passage is formed in the blody I0 'and extends almost entirely through the body from the bottom thereof. Near the top of the body, a radial opening I2 extends inwardly from the periphery of the body and communicates with the upper end of passage |I. A squib I3 is located at the inner end of opening I2 so as to be positioned at the upper end of `passage Il. Wires |4 are provided for operating the squib electrically.

Between the squib and the bottom of the body I0, a cylindrical opening |5 extends into the body from the periphery thereof almost to the passage Il, the opening being provided with a threaded closure member. maat; l'fsfloller: Gnd, New? 12h? center of the bedr. the. opening l5 narrows-t0 form a. .reduced f portion I 1'. which intersectsthe passage I l, the opening l 5..-fl1 extending ihmllsb the major portion yof the. diameter of,v the .haar At the inner end of evening lzadjacent the .er duced portion |1 isa shoulder 2.0;which serves to position a pellet 2| in the opening |15;l the-pellet 2| beingmade .ofmetal or othersutableheat conducting, noninlamrrrable-material. The opte;- end or pellet 2| .fisnoilowedvout at 2.3.15@ receive a.. charge k23 which when ienitedwili heat-tbe pellet.. A sate his slide-bly mcuntedin-openiag |1 and is urged inwardly by a spring 25 which bears against the closed end of reduced opening |1. By means of a fusible element 26, the gate 24 is attached to pellet 2| and is thus retained in the position shown in Fig. 1, in which it closes passage Near the periphery of the top. of the body i0, a cylindrical passage 21 extends downwardly into the body so as to communicate at its lower end with opening |5 near the outer Aend thereof. A threaded plug 28 is provided to close the upper end of passage 21. A plunger 29, pointed at its lower end, is slidably mounted in `passage 21. A cap holder 30 carrying a firing cap 3| is mounted in opening l5 directly below the point where it communicates with passage 21. A spring 32 bears against the lower end of plunger 29 and tends to prevent contact of the plunger with the firing cap 3 I.

In operation, the parts of the device yare initifally in the position shown in Fig. 1 of the drawing, with the gate 24 closing passage which otherwise would provide direct communication between squib I3 and the usual booster charge (not shown). Since the passage is closed by gate 24, the booster cannot be detonated by premature firing of the squib. When the projectile carrying this device is fired from the gun, the force of setback moves plunger 29 downwardly against the pressure of spring 32 until the point of the plunger strikes and fires cap 3| which, in turn, ignites heating charge 23 in pellet 2|. After a predetermined time, pellet 2| becomes heated and conducts a suflicient amount of heat to the fusible element 26 to Isoften or melt the same. When this occurs, gate 24 is free to move outwardly under the action of centrifugal force against the resistance of spring 25, and in so doing opens passage thus arming the fuze. With the gate 24 no longer blocking passage firing of the squib will detonate the booster charge through passage It will be observed that several features of the device prevent premature opening lof the gate 24 to arm the device. Spring 32 prevents contact of the plunger 29 with the cap 3| except when the plunger is `acted upon by a very large force of the magnitude of that produced by setback, thus making the device safe against premature arming by accidental dropping which might otherwise prematurely ignite the charge 23. Should the gate 24 become prematurely detached from pellet 2l by accidental breaking of the fusible member 26, the spring 25 is of sucient strength to hold the gate 24 in its closed position, and the large centrifugal florce generated by a rapidly spinning projectile is necessary to move the gate 24 outwardly against spring 25. Thus, the device is safe against premature amming by tumbling. A5 a result of the incorporation of these safety features, the device will not be armed except when acted upon successively by a force of setback and centrifugal force.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

In a fuze for a rotating projectile, a. substantially cylindrical body having an axial ignition bore, a squib at one end of said bore, said blody having a substantially diametrically located passage intersecting said bore and closed at both 4 ends, a gate member shiftable in said passage. a spring lodged in one end of the passage and urging said gate member into position to close said bore, thereby preventing the transmission of ignition from said squib thnough said bore, a metallic pellet lodged in the other end of said passage, said pellet having a cavity therein, a heat-producing composition in said cavity, a fusible element connecting the inner end of said gate member to the adjacent end of the pellet, and means actuated by setback to ignite said cornposition, thereby heating said pellet and melting the fusible element to release the gate member, which thereupon moves radially outward against the spring, under the influence of centrifugal force, to open the ignition bore.

ROBERT B. BRODE.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,103,014 Palmieri Dec. 21, 1937 FOREIGN PATENTS Number Country Date 22,899 Great Britain 1911 304,258 Germany May 27, 1920 241,941 Great Britain 1925 245,766 Great Britain 1926 

